Recommendations for effective loose parts monitoring

Abstract

Loose parts monitoring systems are used to detect structure borne sound that can indicate the presence of impacting metal parts inside the primary coolant system of commercial nuclear power reactors. Experience with these systems has not been uniform, with cases including high false alarm rates, failure to detect loose parts, and limited capability for interpreting alarms and signals. Utilities have become increasingly aware of benefits that can be obtained from loose parts monitoring as a result of events that damage steam generator tubes, require fuel and reactor internals cleaning, and cause fuel pin failures. A research project, sponsored by the Electric Power Research Institute, used metal impact theory and experimental data to develop a quantitative description of loose part signals as a function of impact, signal transmission, and detection properties. These signal properties were used to develop recommendations for the number, location, and attachment of sensors, and methods for signal processing, recording, impact response calibration, system surveillance, and signal interpretation. Technical considerations and experience link these systems to combined applications for component vibration and rotating equipment monitoring.